1. Field of the Invention
The present invention relates to a data access method, a channel adapter, and a data-access control device which read/write, in response to an instruction from an external apparatus, data to/from a data storing memory that stores variable-length data for each block including predetermined fields.
2. Description of the Related Art
Magnetic disk devices having a data format of variable-length records are used as external storage devices for mainframe systems that run on vender-unique operating systems.
Disk array devices (which are also referred to as “RAID (Redundant Arrays of Inexpensive Disk) devices”) having a configuration that enhances high-speed data access and data-failure resistance are often used as external storage devices used for information processing systems. Since the disk array devices are often used in open systems that run on different types of general-purpose operating systems, they have data formats of fixed-length records.
In recent years, with the advancement of information processing technology, information processing terminals have been widely used, and cases in which an information processing system is configured with a combination of a mainframe system and an open system are increasing. Thus, the disk array device for storing data in a fixed-length data format is configured so as to allow data to be accessed from the mainframe system.
In light of such a situation, for example, Japanese Unexamined Patent Application Publication No. 2006-164141 discloses a data write method for enhancing the reliability of data to be written to a cache memory. In this method, when a variable-length record is written to a cache memory of a CA (channel adapter) that manages data of a fixed-length data record by using a fixed-length, an FCC (field check code) is added to a field of the viable-length record and a BCC (block check code) is added to an LBA (logical block addressing).
Japanese Unexamined Patent Application Publication No. 2003-36146 discloses a disk-array control method. In the disk-array control method, an addition check code is added to data written to disks constituting a parity group of a disk array device and all addition check codes of the parity group are written to a parity disk. During data reading, the addition check codes in the parity disk are read to check data.
Japanese Unexamined Patent Application Publication No. 2006-79380 discloses a disk array device. In the disk array device, part of data to be written to a disk is stored in a management area and computation data generated based on part of the data is embedded in the data to thereby performing writing to the disk. When reading the data from the disk, the disk array device extracts the computation data embedded in the data to perform predetermined computation, and compares the result of the computation with the part of the data stored in the management area to check the validity of the read data.